Ruby programming: .ruby_history file
If anyone else ever wonders why they have the following file: ~/.ruby_history in their home directory, it's because they used Ruby this way:
rlwrap ruby your_ruby_script.rb
rlwrap is a great way to allow command editing from the command line without doing anything fancy in your terminal program. It allows both Emacs-style and Vi-style editing.
Of course, I found this out after I added command logging to my current software project, extbrain. Although the logging I have in my software project is more specific than 'all the input typed in while running rlwrap'.
Of course, this file is a necessary evil, because one of the joys of rlwrap is getting history back.